Question

I have a PictureBox, with an floor plan image.

On that image I would like to draw a polygon, which I can with the following code:

Private points As New List(Of Point)

Private Sub FlorPlan_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles FlorPlan.MouseDown

points.Add(e.Location)
FlorPlan.Invalidate(New Rectangle(e.X, e.Y, 5, 5))
End Sub

Private Sub FlorPlan_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles FlorPlan.Paint
    For Each p As Point In points
        e.Graphics.FillRectangle(Brushes.Red, p.X, p.Y, 5, 5)
    Next
End Sub

Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim myPen As Pen
    myPen = New Pen(Drawing.Color.Red, 2)

    Dim myGraphics As Graphics = PictureBox.CreateGraphics
    myGraphics.DrawPolygon(myPen, points.ToArray)
    'myGraphics.FillPolygon(Brushes.Red, points.ToArray)
    myGraphics.Dispose()
End Sub

What I would like to do is to get hold of that object, so that I later can change the background color, etc.

How should I proceed?

Answer 1

Their are two ways this would typically be done:

• Manually keeping track of all your graphical objects in a list of some custom class.
• Dynamically load a new control for each graphical object.

If you choose to do the latter, I would recommend creating your own UserControl which contains all the necessary data about each graphical object, such as the points in the polygon. To dynamically load them, you could do something like this:

Private Sub AddGraphicalObject(properties As GraphicalObjectProperties)
    Dim control As New GraphicalObjectControl()
    control.Properties = properties
    ' set position and size
    Panel1.Controls.Add(control)
End Sub

You will probably want to add some event handlers to some of the events on the control too as you add them.